Multi-tier defect scan management for memory subsystems
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Solution Overview
Problem
Current defectivity scans in memory sub-systems consume significant time and resources, leading to increased latency and power consumption, and can result in false positive defect detection, necessitating unnecessary remedial operations.
Innovation Solution
Implementing a multi-tiered defect scan management system that performs initial lower-tier scans quickly with reduced accuracy, and only conducts higher-tier scans with increased accuracy when defects are indicated, thereby minimizing unnecessary operations and optimizing resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional defect scans are performed with high accuracy, then defect detection reliability is improved, but scanning time and power consumption increase significantly
Solution Approach 1:
The defect scan is divided into multiple tiers: a first tier using fast, low-accuracy scan patterns for initial screening, and a second tier using slower, high-accuracy scan patterns for verification. This segmentation allows most areas to be quickly screened while only potentially defective areas undergo thorough inspection, resolving the contradiction between speed and reliability.
Solution Approach 2:
Instead of performing full high-accuracy scans on the entire memory device, the system performs partial high-accuracy scans only on areas where defects are suspected based on first-tier results. This partial action maintains reliability for critical defect detection while significantly reducing overall scanning time and power consumption.
2Reliability
If traditional defect scans are performed with high accuracy, then defect detection reliability is improved, but power consumption increases significantly
Solution Approach 1:
The scan process is segmented into low-power first-tier patterns and high-power second-tier patterns. By executing the majority of scans at the first tier level and only escalating to the second tier when necessary, the system maintains defect detection reliability while dramatically reducing average power consumption.
Solution Approach 2:
High-power second-tier scans are performed only partially, specifically on regions where defects are indicated by first-tier scans. This selective application of high-power operations maintains reliability for critical defects while minimizing overall power consumption across the entire scanning process.
3Measurement precision
If high-accuracy scans are performed on all areas, then false positive detection is reduced, but scanning time and resource usage increase
Solution Approach 1:
The scanning process is segmented into two precision levels: first-tier scans with lower precision for rapid coverage, and second-tier scans with high precision for verification. This segmentation reduces false positives by applying high precision only where needed, thereby maintaining measurement precision while improving overall scanning throughput.
Solution Approach 2:
High-precision second-tier scans are applied partially only to areas flagged by first-tier scans rather than uniformly across the entire memory device. This partial application reduces false positive detection while preserving productivity by avoiding unnecessary high-precision scanning of defect-free areas.
Data Source
AI summary
A system can include a processing device operatively coupled with the one or more memory devices, to perform operations that include writing data to the one or more memory devices and performing one or more scan operations on a management unit containing the data to determine a current value of a chosen data state metric. Each scan operation can be performed using a corresponding predetermined read-time parameter value. The operations can include determining whether the current value of the chosen data state metric satisfies a criterion, and can also include, responsive to determining that the current value of the chosen data state metric satisfies the criterion, selecting a remedial operation by determining whether redundancy metadata is included in a fault tolerant data stripe on the one or more memory devices. The operations can also include performing the remedial operation with respect to the management unit.